The major cytokine response to chlamydial salpingitis in the macaque is a Th1 pattern, which may act to minimize scarring and enhance clearance of organisms. Both IFN-(, which has been demonstrated to enhance chlamydiacidal activity in mice, and IL-10, which is considered to suppress immune responses, are produced. We tested the roles of IFN-( and IL-10 in the macaque model. Ectopic autotransplants of macaque salpingeal tissue (subcutaneous "pockets") were inoculated with 1(105 IFU of C. trachomatis serovar E on day 0, then treated with recombinant human (rh) IFN-( or saline by repeated injections on days 3, 4, 5 and 6 post-inoculation. Pockets of an additional macaque were inoculated with chlamydia on day 0, then treated with rhIL-10 or saline by repeated injections on days 2, 3, 4, 5 and 6 post-inoculation. Pockets were examined for inflammatory reactions by light microscopy, for chlamydial MOMP by immunocytochemistry (ICC), and for chlamydial DNA by ligase chain reaction (LCR). Both rhIFN-( and rhIL-10 were associated with a significant increase in PMNs and a tendency towards increased lymphocyte numbers compared with controls. By day 7, infection was decreased by IFN-( treatment during the acute phase of in vivo infection (88% positive on day 5 to 38% positive on day 7). In contrast, IL-10 treatment appeared to interfere with the clearance of chlamydia (67% positive on day 5 to 50% positive on day 7). Thus, there was a trend towards more rapid clearance of organisms with IFN-( treatment, and towards delayed clearance with IL-10 treatment.